With the continuous development of digital photography technology and quality inspection, the demand for image stitching in practical applications is increasing. Traditional image stitching algorithms employ a variety of hand-designed methods for feature extraction, matching, and optimization. However, these traditional feature-based image stitching techniques heavily rely on feature extraction and may not perform well in scenarios with limited features. Current image stitching solutions based on supervised deep learning lack relevant data sets, and labeling data is relatively cumbersome, making supervised deep learning methods unreliable. At the same time, the rise of unsupervised deep learning algorithms provides new ideas for image stitching. We use unsupervised homography estimation to provide information about the geometric relationship between images, Stitching-Domain Transformer Layer to align feature maps, warp and generate masks, it helps to enhance the reality and continuity of splicing. We simultaneously utilize a pre-trained deep learning model (VGG) for feature extraction. We adjust the smoothness loss term to ensure smoother transitions within the stitching areas. Throughout the training process, we continuously optimize the number of convolutional layers, channels, and network depth to achieve optimal results. The superiority of the unsupervised learning algorithm compared to other classic algorithms was verified through experiments. Finally, we discussed the challenges and future applications of unsupervised deep learning in image stitching.
The star sensor is an attitude-sensitive device for spaceflight. It is a critical component in the autonomous attitude determination of aerospace vehicles. Compared to other attitude sensors, the star sensor offers higher attitude accuracy, low power consumption, small volume, and strong autonomy. It plays an important role in high-precision remote sensing, astronomical navigation, and other fields. Star extraction is an essential part of the star sensor in the process of working. Its accuracy and the number of extracted stars affect the performance of the star sensor. This paper proposes a method of star extraction based on the combination of the Improved Optical Flow Method (IOFM) and Dynamic Filtering (DF) named IOFM-DF. Based on the optical flow method, the motion characteristics of stars in the time and space domains are considered. Due to the difference between the star and noise in the motion trajectory, dynamic filtering is used to reduce the influence of noise from the star image on the extraction effect of the star. Considering the statistical properties of the motion trajectories of multiple stars, the cosine distance of the motion track between the extracted point and the star is calculated to predict the probability that the extracted point belongs to the star. IOFM-DF can extract and track stars in the star image for a low signal-to-noise ratio. Experimental results show that IOFM-DF increases the number of star extractions by at least 30% compared to traditional methods. This research is important to improve the accuracy and performance of star sensors.
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